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authorJens Axboe <axboe@fb.com>2017-04-20 14:53:28 -0600
committerJens Axboe <axboe@fb.com>2017-04-20 14:53:28 -0600
commit3a07bb1d7676ea24bc1585ba2a80604852c005e7 (patch)
tree369e7828eca8e73a2d662aa8152fcb9cf4d5120c
parentbe56945c4edd5a3da15f8254b68d1ddb1588d0c4 (diff)
blk-mq: fix potential oops with polling and blk-mq scheduler
If we have a scheduler attached, blk_mq_tag_to_rq() on the scheduled tags will return NULL if a request is no longer in flight. This is different than using the normal tags, where it will always return the fixed request. Check for this condition for polling, in case we happen to enter polling for a completed request. The request address remains valid, so this check and return should be perfectly safe. Fixes: bd166ef183c2 ("blk-mq-sched: add framework for MQ capable IO schedulers") Tested-by: Stephen Bates <sbates@raithlin.com> Signed-off-by: Jens Axboe <axboe@fb.com>
-rw-r--r--block/blk-mq.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 572966f49596..c7836a1ded97 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2928,8 +2928,17 @@ bool blk_mq_poll(struct request_queue *q, blk_qc_t cookie)
hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)];
if (!blk_qc_t_is_internal(cookie))
rq = blk_mq_tag_to_rq(hctx->tags, blk_qc_t_to_tag(cookie));
- else
+ else {
rq = blk_mq_tag_to_rq(hctx->sched_tags, blk_qc_t_to_tag(cookie));
+ /*
+ * With scheduling, if the request has completed, we'll
+ * get a NULL return here, as we clear the sched tag when
+ * that happens. The request still remains valid, like always,
+ * so we should be safe with just the NULL check.
+ */
+ if (!rq)
+ return false;
+ }
return __blk_mq_poll(hctx, rq);
}